It is known design practice to modify an automotive vehicle driveline to adapt it for drag-race applications. This typically would require incorporating a transmission brake function within the transmission housing to lock the transmission in a static condition when the vehicle brakes are applied and the engine throttle is advanced at the initiation of a launch of the vehicle. The internal transmission lock permits the operator to hold the vehicle at the starting line while applying full engine torque. The wheel brakes normally would lack sufficient braking capacity for such conditions.
Such modifications to the transmission for drag-race applications involve extensive redesign of the transmission to accommodate an internal transmission lock. At the instant of the launch, the internal transmission lock is released. This allows maximum launch acceleration to be achieved since the engine is held at its optimum stall speed prior to the launch.
The stall speed of the engine is determined by the torque converter size factor and by the engine torque available. The torque converter size factor, a well known design characteristic, is equal to the engine speed divided by the square root of the turbine torque.
The vehicle brakes and the internal transmission lock are applied as the throttle is advanced to a position at or near the wide-open throttle position. Takeoff or launch occurs as the vehicle brakes and the internal transmission lock are released.
In a typical driveline that has been modified for drag-race applications, the vehicle can be maintained in the stalled state at launch with the engine operating at a higher power level only if additional braking is provided to complement the wheel braking.